Its not just kwaks that suffer from aftermarket pipes being fitted , from experience its the quality of the pipework in terms of internal shape etc . A session on a rolling road and the carbs rejetted may work as if you've fit a full race system it plays hob with the mixture and runs the engines lean.

A mate of mine had exactly the same thing with some budget shite from e-bay for his Honda

There may not be enough back pressure if its a race item as a lot of em are straight through with no lumps n bumps to give any semblence of back pressure. The rolling road bods ll know all this anyhoo.

I had 1 as a track bike ;cracking piece of kit just needed more stomp for my fat gut

its not meant to be a race system and has an arrow can, which was fine on the original pipes,
I'll try the uprated air filter (as its cheap) and it feels like an over fuel problem so more air might help.

and just hope the rolling road will smooth it out fingers crossed,

Any other advise would be great and ill post back after the rolling road

As a general rule if you change the pipes or the air filter you need to rejet. You may not realise you need to rejet if the difference is not great but trust me - you do. Chances are that if you have added parts that are supposed to improve performance (as opposed to just look different, in which case all bets are off) you now run lean and need (as a minimum) a bigger main jet. Balancing the carbs is not the same as re-jetting them.